1. Field of the Invention
The present invention generally relates to a pump jack and more particularly to a pump jack operated by dual hydraulically operated rams each of which includes a piston and cylinder assembly and a control arrangement for controlling the pivotal movement of a walking beam in a manner to render the operation of the pump jack more efficient, with less repair and maintenance and for a longer life expectancy with the pump jack also including a base having a pivotal section adjustable by a brace arrangement to facilitate installation of the pump jack at a well site.
2. Description of the Prior Art
Pump jacks for use in combination with oil wells have been used for many years and most of those presently being used include a pivotal walking beam supported from a stanchion or samson post by a saddle bearing with the end of the beam overlying the oil well having a horse head thereon to which a wire rope or cable bail assembly is connected for securing the walking beam to the upper end of a polish rod for reciprocating the polish rod, sucker rods and downhole pump. The walking beam usually is driven by pitman arms or rods which in turn are connected to eccentric cranks on a crank shaft driven from a prime mover through a reduction gear arrangement with counterbalance devices being associated with the mechanism. Such devices are relatively expensive and heavy in weight due to the large reduction gear unit and counterbalance unit employed thereon and have required substantial maintenance time and repair costs to retain the pump jack in properly adjusted operating condition. Also, such devices exert substantial abrupt tension forces on the polish rod and sucker rods as well as impact forces on the components of the pump jack which has resulted in excessive wear and fatigue breakage of various components.
Efforts have been made to provide fluid power operated piston and cylinder assemblies for operating the pump jack. The following U.S. patents relate to pump jacks and operating mechanisms therefor and which are all cited in my copending application:
U.S. Pat. Nos.:
2,131,910--Vernon et al--October, 1938 PA0 2,232,449--Habenicht--February, 1941 PA0 2,550,723--Ross--May, 1951 PA0 2,704,998--Day et al--March, 1955 PA0 3,175,513--Dulaney--March, 1965 PA0 3,369,490--Hawk--February, 1968 PA0 3,221,568--Ross--December, 1965 PA0 3,405,605--Ross--October, 1968 PA0 3,971,213--Kelley--July, 1976.